Most hinged doors in any building are equipped with door handles. The handles facilitate the manual operation of the latching mechanism and the manual opening and closing of the door. A door handle requires some componentry to facilitate these two functions and typically comprise the following; The handle itself, being a knob or lever with a projecting stem rotatably attached to a mounting plate, generally defined as an escutcheon. The escutcheon provides a bearing for the stem and for attachment to the door, and means provided within the handle stem for rotational actuation of the latch mechanism, usually via mutual engagement with a square section shaft.
The handle and the escutcheon, being visible components, are generally required to have a good appearance and traditionally have been designed, ornamented and finished to maximise their esthetic appeal. Various methods have been devised to improve their appearance by concealing the fixing screws, commonly used to attach the escutcheon to the door. This is generally achieved by providing a mounting plate, which employs the normal screw attachment to the door, and some concealed coupling arrangement which provides for the attachment of the escutcheon to the mounting plate. Examples of this are disclosed in Australian patent 653083 in which a threaded central boss within the escutcheon engages within a central thread of the mounting plate, and the lug and groove twist action of Australian patent 14803/95.
Lever handles are preferable to knobs from a functional point of view, and are the normal form of door handle in most commercial or public premises. Knobs cannot be operated by any means other than hand rotation, and are thus more difficult to operate for persons with some types of disability of the hand. Lever handles are less reliant on the strength of grip and can be easily operated by downward pressure of a hand or even an elbow. However, lever handles are not without disadvantages. A spring is generally required within the mechanism to return the lever after operation to its "at rest" position and to prevent lever droop. Also, the requirement for the lever to be fixed at one end to a stem has meant that the range of lever handle shapes, though often embodying good design, has been quite limited.
Prior art also acknowledges the requirement to include a "privacy" locking function as an option within a door handle product range. This facility is generally required in toilets and bathrooms where the occupant is able to engage the locking function to prevent the accidental intrusion of other persons. Typical examples of this facility are disclosed in U.S. Pat. No. 5,505,508 and Australian patent 653083 wherein the locking function is provided as a separate accessory which is adapted to be installed together with the handle assembly. These patents also, coincidentally, include an example of a concealed handle mounting arrangement mentioned above.